Question

Sexual reproduction in which cells of two different Spirogyra filaments conjugate is known as
a. Lateral conjugation
b. Scalariform conjugation
c. Parthenocarpy
d. Zygospore

Answer 1

Spirogyra is the filamentous green algae, and it got its name because of the helical or spiral arrangement of a chloroplast, and there are almost 400 species of spirogyra in the earth, and they are normally a freshwater habitat.

Complete answer:

General features:
- They are 10 to 100 micrometers in width and they are several centimeters in length.
- They are common in freshwater habitats, and they form slimy filamentous green masses.
- Generally, they grow under the water, and when there is enough sunlight and warmth, they produce a large amount of oxygen.
- And they have a cell wall, nucleus, and spiral-shaped chloroplast.

Reproduction:
In spirogyra, both sexual and asexual reproduction occurs, whereas in sexual reproduction, fragmentation or vegetative propagation takes place, and the division is intercalary.

Sexual reproduction.
Generally, in spirogyra, sexual reproduction is by conjugation, and they are of two types.

- Scalariform conjugation: In this type of conjugation, two or more filaments of spirogyra require, where the filaments are arranged parallel to each other.
The cells of each filament show the protuberance, and this protuberance grows to form the conjugation tube and the conjugation tube of both sides combined and form a conjugation canal. The cell which acts as a male sends its cytoplasm and gametes through a conjugation tube to the female and they fertilize and form the zygospore.

- Lateral conjugation: This type of conjugation occur in the adjacent cells of the one filament with common transverse walls, in which conjugation tubes formed within the wall, and they form a conjugation canal, and there is the transfer of the cytoplasm of the male cell to female and fertilization occurs and zygospore formed. As they asked about two different spirogyras.

Hence, the correct answer is option (B).

Note: The difference between scalariform conjugation and in lateral conjugation is, in the first one conjugation occurs between two or more filaments, while in the lateral conjugation it occurs within the 2 cells of a single filament.